1. Field of the Invention
The present invention relates to a method for fabricating a semiconductor device, and a more particularly, to a method for fabricating a semiconductor device, which allows the cell current of the semiconductor device to be increased.
2. Description of the Prior Art
Among the properties of a semiconductor device, cell current is generally connected with tWR (Write Recovery time) margin failure. If tWR margin is insufficient, the write margin of stored information will be insufficient and thus write failure will occur.
In the prior art, to increase cell current, there is used a method of increasing the doping concentration of plugs, or a method of performing an ion implantation process after forming the plugs.
In such a prior art, since a rapid thermal annealing (RTA) process is performed before forming the plugs, out-diffusion effect from the plug is insignificant and thus an increase in cell current is also insufficient.
To increase cell current, an additional ion implantation process is also frequently performed after forming the plug. In this case, however, since this ion implantation process is performed at low temperature, it has an insignificant effect on the increase of cell current.
Namely, as a device becomes fine, channel doping concentration is increased. Thus, the prior method encounters a limitation in increasing the cell current of the device.
Furthermore, in developing a 110 nm device, the prior method ensures only a cell current of 25-30 μA without satisfying the cell current requirement of 37 μA or more in products. Thus, the prior method has a problem in that tWR bit failure occurs in several thousands of bits.